Friday, February 26, 2016

Linux bridge, macvlan, ipvlan, adapters

The open source Host sFlow project added a feature to efficiently monitor traffic on Linux host network interfaces: network adapters, Linux bridge, macvlan, ipvlan, etc. Implementation of high performance sFlow traffic monitoring is made possible by the inclusion of random packet sampling support in the Berkeley Packet Filter (BPF) implementation in recent Linux kernels (3.19 or later).

In addition to the new BPF capability, hsflowd has a couple of other ways to monitor traffic:
  • iptables, add a statistic rule to the iptables firewall to add traffic monitoring
  • Open vSwitch, has built-in sFlow instrumentation that can be configured by hsflowd.
The BPF sampling mechanism is less complex to configure than iptables and can be used to monitor any Linux network device, including: network adapters (e.g. eth0) and the Linux bridge (e.g. docker0). Monitoring a network adapter also provides visibility into lightweight macvlan and ipvlan network virtualization technologies that are likely to become more prevalent in the Linux container ecosystem, see Using Docker with macvlan Interfaces.

The following commands build and install hsflowd on an Ubuntu 14.03 host:
sudo apt-get update
sudo apt-get install build-essential
sudo apt-get install libpcap-dev
sudo apt-get install git
git clone
cd host-sflow
sudo make install
Installing Host sFlow on a Linux server provides basic instructions for configuring the Host sFlow agent (hsflowd). To monitor traffic on the host, edit the /etc/hsflowd.conf file configure the sFlow collector and enable packet sampling on eth0
pcap { dev = eth0 }
Now start the daemon:
sudo hsflowd start
At this point packet traversing eth0 will be sampled and sent out as part of the standard sFlow telemetry stream sent to an sFlow analyzer. For example, using sFlow-RT with the top-flows application as the sFlow analyzer generated the top flows table below.
There a numerous server monitoring agents available in the open source community that will export similar host statistics (CPU, memory, disk) to the Host sFlow agent. Host sFlow differs by also including network traffic visibility using the same packet sampling mechanism supported by most data center switches. Significant advances are extending the visibility into the physical network, for example, Broadcom BroadView Instrumentation tracks buffer utilization and microbursts that effect application performance.
A common standard for monitoring physical and virtual network and server infrastructure reduces operational complexity. Visibility into network activity is critical to understanding the performance of scale out applications that drive large amounts of East-West traffic. Host sFlow, along with support for sFlow in the physical network, delivers scaleable data center wide telemetry to SDN and DevOps tools so that they can better orchestrate the allocation of resources to maximize performance and reduce costs.

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